Japanese Patent Application Publication No. 2009-092137 (hereinafter referred to as Patent Document 1) discloses a well-known liquid-sealed vibration damping device in the same category as the present disclosure. This liquid-sealed vibration damping device is arranged with a circular partition member that partitions a main liquid chamber and an auxiliary liquid chamber so as to absorb the internal pressure in the main liquid chamber.
This liquid-sealed vibration damping device includes a first mounting part that is mounted on the engine and a second mounting part that is mounted on the vehicle body, wherein an insulator is interposed between the first and second mounting parts. The second mounting part is an outer cylindrical member that is arranged so as to surround the periphery of the insulator, and includes a first frame and a second frame that is connected to the first frame. The partition member is arranged under the first frame. The second frame covers the periphery of the partition member.
The first frame is formed to have recesses for engagement on the outer peripheral surface along the circumferential direction. In contrast, the second frame is formed to have claw-shaped protrusions to be engaged with the recesses of the first frame. The outer cylindrical member is easily assembled by engaging the protrusions of the second frame with the recesses of the first frame.
Incidentally, as an engine room of a vehicle is designed smaller, a liquid-sealed vibration damping device is also required to be smaller. In general, a liquid-sealed vibration damping device, inclusive of the one disclosed in Patent Document 1, has a circular outer shape in a plan view, likely to cause space efficiency to be reduced. Then, as a result of taking space saving into account, a liquid-sealed vibration damping device has been studied that has a substantially quadrangular outer shape in a plan view. In this liquid-sealed vibration damping device, the partition member is preferably formed also to have a substantially quadrangular shape in a plan view to secure an area for obtaining high damping performance.
Normally, forming an outer cylinder member so as to have a substantially quadrangular shape in a plan view makes corners of the outer cylinder member to have high rigidity, while it makes linear sections of the same to have lower rigidity than the rigidity on the corners. This causes a problem that, if the outer cylinder member is formed to have a structure of engaging the protrusions of the second frame with the recesses of the first frame as with the above-described Patent Document 1, the protrusions will have variations in rigidity to create difficulty in making an interference margin between the first and second frames substantially uniform in the circumferential direction. This problem is not limited to a liquid-sealed vibration damping device having the outer cylindrical member formed in a substantially quadrangular shape in a plan view, and rather it is a common problem which also occurs in a liquid-sealed vibration damping device inclusive of any outer cylindrical member in a shape of having linear parts and corners which continue to the linear parts.
A solution is needed that can solve the above-identified problems to provide a liquid-sealed vibration damping device that allows an outer cylindrical member to have a substantially uniform interference margin in the circumferential direction, while improving an assembling property.